This proposal is responsive to the topics of definition and recognition of cardiac states at high risk of arrhythmias and sudden cardiac death. Electrocardiographic wave-form is proposed for the recognition of such states under the general rationale that electrophysiologic abnormalities responsible for arrhythmia susceptibility are also determinants of electrocardiographic waveform. Definition of high risk cardiac states in terms of conduction, excitability and recovery is proposed. The proposal to improve recognition and further define vulnerable cardiac states both includes simultaneous recording from large electrode arrays, special consideration of autonomic factors in cardiac states vulnerable to arrhythmias and subject to sudden death and emphasis on ventricular repolarization in vulnerable cardiac states and their recognition by electrocardiography.